In FIG. 7, a cross-sectional view of a conventional thrust roller tearing showing only the upper parts is illustrated. The thrust roller bearing comprises an inner race 1, an outer race 2, needle rollers 3, and a retainer 4 for keeping the needle rollers 3 positioned for rotation.
The inner race 1 is provided with a race body 5 composed of a circular thin plate, a cylindrical portion 6 extending axially from the inner periphery of the body 5, and a circular projection 7, disposed at the edge of the cylindrical portion 6 and bent radially outwardly, for preventing detachment of the retainer 4. The outer race 2 is provided with a race body 8 composed of a circular thin plate, a cylindrical portion 9 extending axially from the outer periphery of the race body 8, and a circular projection 10, disposed at the edge of the cylindrical portion 9 and bent radially inwardly for preventing detachment of the retainer 4.
The retainer 4 comprises a pair of circular plates 11 and 12 having a cup-shape cross-section. Each of the pair of circular plates 11 and 12 has a plurality of circumferentially separated pockets. Needle rollers 3 are supported in the pockets of the retainer 4. The retainer 4 is interposed between the inner race 1 and the outer race 2, so that the retainer 4 cannot be separated from the inner race 1 and the outer race 2 with the help of the circular projection 7 of the inner race 1 and the circular projection 10 of the outer race 2.
The above-described thrust roller bearing A operates by being interposed between a vertical face 13a of a shaft 13 and a vertical face 14a of a housing 14. The shaft 13 and the housing 14 rotate relative to one another. For example, the shaft 13 is provided with a circular race rest 15 which engages the cylindrical portion 6 of the inner race 1 of the thrust roller bearing A. The back of the race body 5 of the inner race 1 rests against the vertical face 13a of the shaft 13. The back of the race body 8 of the outer race 2 rests against the vertical face 14a of the housing 14.
As an example, the thrust roller bearing A can be used in an automatic transmission as illustrated in FIG. 7. In such an example, the shaft 13 and the housing 14 may be separated from each other in the direction of their axes. Therefore, a load may or may not be applied on the thrust roller bearing A interposed between the shaft 13 and the housing 14.
When the shaft 13 is separated from the housing 14 in the direction of their axes and the load is not applied on the thrust roller bearing A, the thrust roller bearing A is removed from the race rest 15 of the shaft 13 with the thrust roller bearing A being close to the housing 14 and, finally, the bearing A detaches from the shaft 13 and the housing 14 as illustrated in FIG. 8. This is caused by coherency of a lubricant interposed between the vertical face 14a of the housing 14 and the back of the outer race 2 of the thrust roller bearing A.